1. Field of the Invention
The present invention is directed to an x-ray computed tomography apparatus of the type having an elongated anode that is scanned by an electron beam for generating a traveling x-ray beam, this electron beam being generated by an electron gun, wherein the electron beam is deflected onto and guided along the anode by a magnet arrangement.
2. Description of the Prior Art
U.S. Pat. No. 5,548,630 discloses an x-ray computed tomography apparatus of the above general type.
An x-ray computed tomography apparatus with electronic scanning of an annular anode is also disclosed in U.S. Pat. No. 5,247,556.
Given a low space requirement, such computed tomography apparatuses enable an especially fast scanning of an examination subject because the focus is electronically guided around the anode. A static guidance field that holds the electrons on the predetermined circular orbit and a dynamic kick field that deflects the electrons onto the ring anode in the desired location are required for guidance and deflection of the electron beam.
Solenoid focusing can be provided so that the electron beam is kept constant in cross-section and so that a constant focal spot is achieved along the ring anode, this solenoid focusing being effected by a solenoid coil arranged along the ring-shaped path for the electron beam. This solenoid coil surrounds the ring anode.